Should you drink water first thing in the morning?

2026-10-30

Yes, drinking a glass of water when you wake up is a sensible habit, but mostly for an unglamorous reason: you have gone seven or eight hours without drinking, and a morning glass is an easy, reliable way to start working toward your daily total. The bigger promises you see online (that morning water "kickstarts your metabolism", "flushes toxins" or melts fat) are not supported by good evidence. Here is what is actually going on, and how to make the habit useful.

What happens to your body's water overnight

While you sleep, you keep losing water: through your breath, through your skin, and through urine your kidneys keep producing, more slowly than during the day. You don't drink anything to replace it. That is why your first urine of the day is usually darker and more concentrated than later urine. It's normal and not, on its own, a sign that something is wrong (see what your urine color says about your hydration).

Your body is prepared for this. The hormone vasopressin (also called antidiuretic hormone) helps your kidneys hold on to water at night, which is part of why most people don't need to get up to pee. Interestingly, a large observational study of more than 20,000 US and Chinese adults found that people who regularly slept about six hours had more concentrated urine and 16–59% higher odds of being inadequately hydrated than people who slept eight hours. The authors suggested that cutting sleep short may cut short a window of vasopressin release. It's an association, not proof of cause, but it is one more reason a glass of water after a short night is reasonable.

What's true about morning water

It's an easy win for your daily total

Most adults need roughly 2 to 2.5 liters of total water a day from food and drinks, according to EFSA (more in heat or with exercise; see how much water you should drink a day). Spreading that across the day is much easier than catching up in the evening. A glass of 8–16 fl oz (250–500 ml) with breakfast gets you 10–20% of the way before you've even left the house.

It anchors a habit

The morning routine is the most predictable part of most people's day. Attaching a glass of water to something you already do (switching off the alarm, starting the kettle, brushing your teeth) is a textbook way to build a habit, because the cue is already there. More on that in how to make drinking water a habit.

It can help if you wake up thirsty or with a dry mouth

If you feel thirsty, slightly headachy or groggy after a warm night, a late dinner, a salty meal or a few drinks the evening before, water first thing is a perfectly good response. Thirst is a reliable signal for healthy adults; you don't need to override it, just answer it.

What's hype

"It boosts your metabolism by 30%"

This claim traces back to a 2003 study of 14 healthy adults in which drinking 500 ml (about 17 fl oz) of water raised metabolic rate by about 30% for an hour or so. It was widely reported. Later, more carefully controlled studies could not reproduce anything close to that. A 2006 study found no increase in energy expenditure after room-temperature water and only about a 4.5% rise after ice-cold water, and a 2015 reassessment concluded that drinking purified water does not meaningfully stimulate thermogenesis or fat burning. Whatever the effect is, it's tiny, and it has nothing to do with the time of day.

"It flushes out toxins"

Your kidneys and liver clear waste products around the clock. Drinking enough water across the day keeps your kidneys working comfortably, but there is no special morning cleansing effect, and drinking extra beyond your needs simply produces more, paler urine.

"Warm lemon water on an empty stomach"

Warm water, lemon water or plain cold water from the tap all hydrate you equally well. Choose the one you'll actually drink. If you add lemon every morning, it's worth knowing that acidic drinks can soften tooth enamel; drinking it with a meal or rinsing with plain water afterwards is a common dentist tip.

"You must drink before coffee, because coffee dehydrates you"

Your morning coffee or tea counts toward your fluids too. At the amounts most people drink, caffeine's mild diuretic effect does not cancel out the water in the cup (see does coffee dehydrate you?). There's no harm in having water first, but it isn't required.

How much to drink in the morning

There is no magic number. A practical range for most adults is one or two glasses, about 8–16 fl oz (250–500 ml), within the first hour or so after waking. A few points:

Don't chug a liter. Your body handles moderate amounts best, and a large volume all at once mostly ends up in the bladder within a couple of hours.
Sip if you're queasy. Some people feel uncomfortable drinking a lot on an empty stomach. Room-temperature water and slower sipping usually help.
Keep going after breakfast. The morning glass is a start, not a substitute for drinking during the rest of the day.
Exercising in the morning? Starting a workout already low on fluids is worth avoiding, so a morning glass matters a bit more on training days. Details in how much to drink before, during and after exercise.

If you have heart failure, kidney disease or another condition where your doctor has limited your fluids, follow their advice rather than general tips.

Making the habit stick

Put the water where you'll see it. A full glass or bottle on the bedside table or next to the kettle removes all friction.
Tie it to an existing step. "After I turn off my alarm, I drink a glass of water" works better than "I'll try to drink more in the morning".
Make it pleasant. Cold, room temperature, sparkling or with a slice of fruit; whatever you like.
Log it. Seeing the first entry of the day makes it more likely you'll keep going.

With Water Tracker, that first glass is one tap on your iPhone, on a Home Screen widget, or on your Apple Watch before you've even picked up your phone. It also suggests a daily goal based on your weight and activity, so you can see how much of it the morning glass already covers.

The bottom line

A glass of water in the morning is a good, low-effort habit: it replaces some of the water you lost overnight, gives your daily total a head start and is easy to remember. It does not meaningfully boost your metabolism, detox your body or burn fat, and it doesn't need to be warm, lemony or on a strictly empty stomach. Drink one or two glasses when you wake up, then keep sipping through the day.

This article is general information, not medical advice. If you have a health condition, are pregnant or take medication, ask your doctor how much you should drink.